Electromagnetically actuatable valves are used in various areas of technology. For example, such valves are necessary for the operation of modern braking systems, hydraulic camshaft adjusting devices or automatic transmissions in motor vehicles. The armature of an electromagnetic actuating device necessary for mechanically actuating the setting piston of such a valve is in this instance, for example, axially movably mounted in an armature guide tube. Alternatively, it is known to provide the armature radially outside with sliding rings and to axially movably situate the armature within a guide cylinder.
The publication WO 2010/009 966 A1 describes an electromagnetic actuating device for a hydraulic control valve of a camshaft adjusting device. This adjusting device has an armature and a first and a second magnet yoke, each of which has a cup-shaped geometry. The first and the second magnet yoke are situated one after the other and in such a way that their open ends face each other. In this instance, the two magnet yokes keep an axial distance to each other so that a ring-shaped air gap is formed between the magnet yokes. Moreover, the two magnet yokes radially inside delimit at least one armature chamber in which the armature is accommodated in an axially movable manner. At a first axial end section of the cylindrical armature facing the first magnet yoke, an axially projecting stop sleeve is inserted into a centric through-hole of the armature, with the aid of which an axial adhesion of the armature to the first magnet yoke is preventable. With the aid of a sliding ring accommodated in a ring groove of the armature, the first axial end section of the armature is radially mounted at an inner circumferential surface of the first magnet yoke. In a second end section of the cylindrical armature directed away from the first end section, a plunger is attached in a through-hole. This plunger is axially movably accommodated in a sliding sleeve and by its free end acts upon an actuator piston of the hydraulic control valve. The sliding sleeve is attached in a coaxial hole within the base of the second cup-shaped magnet yoke. As a result, the armature is axially on both sides radially mounted in the armature chamber.
Even though this electromagnetic actuating device is quite advantageously constructed, it still has the disadvantage that, in order to prevent the axial adhesion of the armature to the base of the first cup-shaped magnet yoke, a stop sleeve is attached at the armature and a sliding ring is situated in a ring groove of the armature for radially mounting the armature in the armature chamber. Moreover, the sliding ring causes an enlargement of the necessary radial installation space of the actuating device, and the sliding ring may have disadvantageous production-related dimensional deviations. Furthermore, the sliding ring enlarges a comparably large radial, parasitic air gap within the electromagnetic actuating device.